Dasher is a computer accessibility tool enabling users to enter text efficiently using a pointing device rather than a keyboard. It has been likened to an arcade game, since to use it you zoom through characters that fly across the screen. It uses a probabilistic predictive model to give priority to more likely character combinations. Dasher can be described as a back-to-front version of arithmetic coding, a data-compression algorithm. Dasher works in all the languages of the world.

Dasher is licensed under the GPL. It is available for several platforms including Linux, Microsoft Windows, and Pocket PC.

Dasher was invented by David J.C. MacKay and developed by David Ward and other members of MacKay's Cambridge research group. The Dasher project is supported by the Gatsby Charitable Foundation.

Dasher takes advantage of Fitts' law -- the fact that larger areas can be selected more quickly than smaller areas.

External links

• The Dasher Project
• The on-line textbook: Information Theory, Inference, and Learning Algorithms, by David J.C. MacKay, explains arithmetic coding in Chapter 6.

References

• David J.C. MacKay (2003) Information theory, inference and learning algorithms, CUP, ISBN 0521642981, (also available online)

User interface | Assistive technology | Free software | GNOME

Dasher